In accordance with a rapid spread of information related apparatuses and communication apparatuses such as a personal computer, a video camera and a portable telephone in recent years, the development of a battery to be utilized as a power source thereof has been emphasized. The development of a high-output and high-capacity battery for an electric vehicle or a hybrid automobile has been advanced also in the technical field such as the automobile industry. A lithium battery has been presently receiving attention from the viewpoint of a high energy density among various kinds of batteries.
Organic liquid electrolyte having a flammable organic solvent as a solvent thereof is used for a presently commercialized lithium battery, so that the installation of a safety device for restraining temperature rise during a short circuit and the improvement in structure and material for preventing the short circuit are necessary therefor. On the contrary, with regard to an all solid lithium battery all-solidified by replacing the liquid electrolyte with a solid electrolyte, the flammable organic solvent is not used in the battery. Accordingly, the simplification of the safety device is promoted and thereby the battery attains excellent production cost and productivity.
An oxide solid electrolyte has been known as an example of such a solid electrolyte. With regard to the oxide solid electrolyte, Li7La3Zr2O12 as a garnet-type compound is disclosed in Nonpatent Document 1, for example. Since Li7La3Zr2O12 has high in Li ion conductivity as bulk, it is effective for achieving higher output of a battery. The garnet-type compound (a solid ion conductor) is disclosed also in Patent Document 1. On the other hand, it is described in Patent Document 2 that the flexibility of a solid electrolyte layer is secured by adding an organic polymer compound into the solid electrolyte layer.